G proteins couple the receptors for a vast array of first messengers to a variety of second messenger systems which generate diverse biological effects. The study of these molecules in vivo has been limited to cell culture systems and the description of pathological conditions which alter the level or function of G proteins. A system does not currently exist ni which the role of these molecules in complex biological processes can be addressed in a systematic way. We intend to analyze the role of G proteins in these processes in the fruit fly, Drosophila. Preliminary studies have involved the characterization of the G proteins present in the adult fly CNS and the isolation of cDNAs from fly head libraries which code for proteins highly homologous to each of the main classes of G protein a subunit expressed in vertebrates. We will extend these studies by isolating and characterizing the genes coding for these cDNAs to determine their potential for the production of alternate transcripts. Antibodies will be generated to peptides specific for each of the G alpha subunit protein to provide us with tools to examine the distribution and expression of each protein during nervous system development. We will attempt to determine the functional homology between fly Gs alpha-like clones and the vertebrate equivalents by assessing the ability of fly cDNAs for this protein to complement the defect present in S49 cyc- cells. The maternal expression of several of the fly G protein alpha subunits will be manipulated to assess the role of these proteins in the early nervous system development. Using the genetic tools available in Drosophila, we will attempt to isolate mutations which abolish the expression of fly G alpha subunits. Such mutations will be studied in their own right and provide us with recipient strains in which to express G protein alpha subunit genes which have been altered in vitro buy site specific mutagenesis and other methods. Using the system we will establish, G proteins will be, for the first time, subjected to study by a number of combined approaches in vivo to determine the role they play in nervous system function and development.